Cobalt catalysts, and use thereof for the conversion of methanol and for Fischer-Tropsch synthesis, to produce hydrocarbons

ABSTRACT

A zirconium, hafnium, cerium or uranium promoted cobalt catalyst and process for the conversion of methanol or synthesis gas to hydrocarbons. Methanol is contacted, preferably with added hydrogen, over said catalyst, or synthesis gas is contacted over said catalyst to produce, at reaction conditions, an admixture of C 10  + linear paraffins and olefins. These hydrocarbons can be further refined to high quality middle distillate fuels, and other valuable products such as mogas, diesel fuel, and jet fuel, particularly premium middle distillate fuels of carbon number ranging to about C 20 .

This is a division of application Ser. No. 922,885, filed Oct. 24, 1986,which is a division of application Ser. No. 813,918 filed Dec. 27, 1985,now U.S. Pat. No. 4,663,305.

BACKGROUND OF THE INVENTION

I. Field of the Invention

This invention relates to improvements in a process for the conversionof methanol to hydrocarbons, to improvements in a Fischer-Tropschprocess for the production of hydrocarbons, and to improvements made incatalysts employed to conduct such processes. In particular, it relatesto improved cobalt catalysts, and process for using such catalysts inthe conversion of methanol, and Fischer-Tropsch synthesis to producehydrocarbons, especially C₁₀ +distillate fuels, and other valuableproducts.

II. Background

A need exists for the creation, development, and improvement ofcatalysts and processes, useful for the conversion of methanol andsynthesis gases to hydrocarbons, especially high quality transportationfuels. Methane is available in large quantities, either as anundesirable by-product or off-gas from process units, or from oil andgas fields. The existence of large methane, natural gas reserves coupledwith the need to produce premium grade transportation fuels,particularly middle distillate fuels, thus poses a major incentive forthe development of new gas-to-liquids processes. However, whereastechnology is available for the conversion of natural gas to methanol,in order to utilize this technology there is a need for new or improvedcatalysts, and processes suitable for the conversion of methanol to highquality transportation fuels, particularly middle distillate fuels.

The technology needed to convert natural gas, or methane, to synthesisgas is also well established. It is also known that synthesis gas can beconverted to hydrocarbons via Fischer-Tropsch synthesis, though new orimproved catalysts, and processes for carrying out Fischer-Tropschreactions are much needed. Fischer-Tropsch synthesis for the productionof hydrocarbons from carbon monoxide and hydrogen is well known in thetechnical and patent literature. Commercial units have also beenoperated, or are being operated in some parts of the world. The firstcommercial Fischer-Tropsch operation utilized a cobalt catalyst, thoughlater more active iron catalysts were also commercialized. An importantadvance in Fischer-Tropsch catalysts occurred with the use ofnickel-thoria on Kieselguhr in the early thirties. This catalyst wasfollowed within a year by the corresponding cobalt catalyst, 100 Co:18ThO₂ :100 Kieselguhr, parts by weight, and over the next few years bycatalysts constituted to 100 Co:18 ThO₂ :200 Kieselguhr and 100 Co:5ThO₂ :8 MgO:200 Kieselguhr, respectively. The Group VIII non-noblemetals, i.e., iron, cobalt, and nickel, have been widely used inFischer-Tropsch reactions, and these metals have been promoted withvarious other metals, and supported in various ways on varioussubstrates. Most commercial experience has been based on cobalt and ironcatalysts. The cobalt catalysts, however, are of generally low activitynecessitating a multiple staged process, as well as low synthesis gasthroughput. The iron catalysts, on the other hand, are not reallysuitable for natural gas conversion due to the high degree of water gasshift activity possessed by iron catalysts. Thus, more of the synthesisgas is converted to carbon dioxide in accordance with the equation: H₂+2CO→(CH₂)_(x) +CO₂ ; with too little of the synthesis gas beingconverted to hydrocarbons and water as in the more desirable reaction,represented by the equation: 2H₂ +CO→(CH₂)_(x) +H₂ O.

The need for a catalyst composition, and process useful for theconversion of methanol or synthesis gas at high conversion levels, andat high yields to premium grade transportation fuels, particularlywithout the production of excessive amounts of carbon dioxide, were metin large part by the novel catalyst compositions, and processesdescribed in U.S. application Ser. Nos. 626,013; 626,023; and 626,026,filed June 29, 1984, by Payne and Mauldin; now U.S. Pat. Nos. 4,542,122,4,595,703, and 4,556,752. The preferred catalysts therein described arecharacterized as particulate catalyst compositions constituted of atitania or titania-containing support, preferably a titania supporthaving a rutile:anatase content of at least about 2:3, upon which thereis dispersed a catalytically active amount of cobalt, or cobalt andthoria. These catalyst compositions possess good activity and stabilityand can be employed over long periods to produce hydrocarbons frommethanol, or to synthesize hydrocarbons from carbon monoxide andhydrogen.

These cobalt-titania catalysts it was found, like most hydrocarbonsynthesis catalysts, became coated during an "on-oil" run with acarbonaceous residue, i.e., coke, formed either during extended periodsof operation or during feed or temperature upsets. The initially highactivity of the catalysts declines during the operation due to the cokedeposits thereon, and the operating temperature must be increased tomaintain an acceptable level of conversion. Eventually the catalystsbecome deactivated to a point where the temperature required to maintainan acceptable conversion level causes excessive formation of methane andother light hydrocarbon gases at the expense of the desired C₁₀+hydrocarbons, at which point it becomes necessary to regenerate, andreactivate the catalyst. Unlike many other catalysts commonly used bythe refining industry however, when the coke deposits were burned fromthe cobalt-titania catalysts at oxidizing conditions by contact with air(or oxygen) at elevated temperatures, and the catalysts thereaftertreated with hydrogen to reduce the cobalt metal component, theinitially high activity of the cobalt-titania catalysts did not returnto that of a fresh catalyst. Rather, their activity was considerablyless than that of fresh cobalt-titania catalysts. Moreover, after theregeneration, and reactivation of the catalysts, there was noimprovement in the rate of deactivation and the deactivation proceededfrom a lower initial activity. This loss in the overall activity broughtabout by burning the coke from these catalysts at elevated temperaturesin the presence of air (oxygen) is not only detrimental per se, butseverely restricts the overall life of the catalyst, and threatens theirfull utilization in commercial operations.

III. Objects

It is, accordingly, a primary objective of the present invention toobviate this problem.

In particular, it is an object to provide novel and improvedcobalt-titania catalysts, and processes utilizing such catalysts, forthe conversion of methanol or synthesis gas to high qualitytransportation fuels, especially distillate fuels characterizedgenerally as admixtures of C₁₀ +linear paraffins and olefins.

A more specific object is to provide new and improved supportedcobalt-titania catalysts, which in methanol conversion andFischer-Tropsch synthesis reactions are not only highly active andstable prior to regeneration, and reactivation, but capable afterregeneration, and reactivation, of recovering their initial highactivity, while maintaining their stability.

A further object is to provide a process which utilizes such catalystsfor the preparation of hydrocarbons, notably high quality middledistillate fuels characterized generally as admixtures of linearparaffins and olefins, from methanol, or from a feed mixture of carbonmonoxide and hydrogen via the use of such catalysts.

IV. The Invention

These objects and others are achieved in accordance with the presentinvention which, in general, embodies:

(A) A particulate catalyst composition constituted of titania, or atitania-containing support, on which there is dispersed a catalyticallyactive amount of cobalt sufficient to provide good activity andstability in the production of hydrocarbons from methanol, or in theproduction of hydrocarbons via carbon monoxide-hydrogen synthesisreactions, and sufficient of a metal promoter selected from the groupconsisting of zirconium, hafnium [i.e., Group IVB metals of the PeriodicTable of the Elements (E. H. Sargent & Co., Copyright 1962, Dyna-SlideCo.) having an atomic weight greater than 90] cerium (a lanthaniumseries metal), and uranium (an actinium series metal), or admixture ofthese metals with each other or with other metals, such that afteroxidizing the cobalt at elevated temperature, as occurs after thedeposition of coke thereon during an operating run, the catalyst can beregeneratedr by burning the coke therefrom by contact at elevatedtemperature with oxygen or an oxygen-containing gas (e.g., air), andthen reactivated by contact of the catalyst with a reducing gas,particularly hydrogen, to reduce the cobalt metal component such thatthe activity and stability of the catalyst is thereby restored.Suitably, in terms of absolute concentrations the cobalt is present inamounts ranging from about 2 percent to about 25 percent, preferablyfrom about 5 percent to about 15 percent, calculated as metallic metalbased on the total weight of the catalyst composition (dry basis). Thezirconium, hafnium, cerium, or uranium in the form of a salt or compoundof said promoter metal, is added to the cobalt-titania catalyst, inamount sufficient to form a catalyst composite the activity andstability of which after regeneration, and reactivation, approximatesthat of a fresh cobalt-titania catalyst, i.e., a catalyst,cobalt-titania catalyst which has never been regenerated. The promotermetal is quite effective in low concentrations, concentrations greaterthan that required to provide the desired regenerability generallyoffering little, or no further benefit. The efficiency of the promotermetals is believed generally related to their highly dispersed physicalstate over the surface of the titania support. Suitably, acobalt-titania catalyst can be made regenerable by compositing therewitha zirconium, hafnium, cerium, or uranium metal in weight ratio ofmetal:cobalt greater than about 0.010:1, preferably from about 0.025:1to about 0.10:1. One of more of said promoter metals--viz., zirconium,hafnium, cerium, or uranium--is dispersed with the catalytically activeamount of cobalt upon a titania support, particularly a titania supportwherein the rutile:anatase weight ratio is at least about 2:3. Therutile:anatase ratio is determined in accordance with ASTM D 3720-78:Standard Test Method for Ratio of Anatase to Rutile in Titanium DioxidePigments By Use of X-Ray Diffraction. The absolute concentration of thecobalt and promoter metal is preselected to provide the desired ratio ofthe zirconium, hafnium, cerium, or uranium metal:cobalt. Zirconium is apreferred Group IVB metal in terms of its cost-effectiveness, and acobalt-titania catalyst to which zirconium is added in weight ratio ofzirconia:cobalt greater than 0.010:1, preferably from about 0.04:1 toabout 0.25:1 has been found to form a catalyst which is highlyregeneration stable. This catalyst has been found capable of continuedsequences of regeneration with essentially complete recovery of itsinitial activity when the catalyst is returned to an on-oil operation,and there is no loss in stability in either methanol conversion orhydrocarbon synthesis reactions. The cobalt-titania catalystcompositions when stabilized with any one, or admixture of zirconium,hafnium, cerium, or uranium, it has been found, produce a product whichis predominately C₁₀ +linear paraffins and olefins, with very littleoxygenates. These promoted catalyst species provide essentially the samehigh selectivity, high activity, and high activity maintenance afterregeneration in methanol conversion, or in the conversion of the carbonmonoxide and hydrogen to distillate fuels, as freshly preparedunpromoted cobalt-titania catalysts (i.e., catalysts otherwise similarexcept that no zirconium, hafnium, cerium or uranium have beencomposited therewith) which have never been regenerated, or subjected toregeneration conditions. The promoted cobalt-titania catalysts are thushighly regeneration stable, the activity and stability of the promotedcatalyst being restored after regeneration to that of an unpromotedcobalt-titania catalyst which has never been regenerated by burning offthe coke at high temperature in air under oxidizing conditions.

(B) A process wherein the particulate zirconium, hafnium, cerium, oruranium promoted cobalt-titania catalyst composition of (A), supra, isformed into a bed, and the bed of catalyst contacted at reactionconditions with a methanol feed, or feed comprised of an admixture ofcarbon monoxide and hydrogen, or compound decomposable in situ withinthe bed to generate carbon monoxide and hydrogen, to produce a middledistillate fuel product constituted predominately of linear paraffinsand olefins, particularly C₁₀ +linear paraffins and olefins.

(i) In conducting the methanol reaction the partial pressure of methanolwithin the reaction mixture is generally maintained above about 100pounds per square inch absolute (psia), and preferably above about 200psia. It is often preferable to add hydrogen with the methanol.Suitably, methanol and hydrogen are employed in molar ratio of CH₃ OH:H₂above about 4:1, and preferably above 8:1, to increase the concentrationof C₁₀ +hydrocarbons in the product. Suitably, the CH₃ OH:H₂ molarratio, where hydrogen is employed, ranges from about 4:1 to about 60:1,and preferably the methanol and hydrogen are employed in molar ratioranging from about 8:1 to about 30:1. Inlet hydrogen partial pressurespreferably range below about 80 psia, and more preferably below about 40psia; inlet hydrogen partial pressures preferably ranging from about 5psia to about 80 psia, and more preferably from about 10 psia to about40 psia. In general, the reaction is carried out at liquid hourly spacevelocities ranging from about 0.1 hr⁻¹ to about 10 hr⁻¹, preferably fromabout 0.2 hr⁻¹ to about 2 hr⁻¹, and at temperatures ranging from about150° C. to about 350° C., preferably from about 180° C. to about 250° C.Methanol partial pressures preferably range from about 100 psia to about1000 psia, more preferably from about 200 psia to about 700 psia.

(ii) The synthesis reaction is generally carried out at an H₂ :CO moleratio of greater than about 0.5, and preferably the H₂ :CO mole ratioranges from about 0.1 to about 10, more preferably from about 0.5 toabout 4, at gas hourly space velocities ranging from about 100 V/Hr/V toabout 5000 V/Hr/V, preferably from about 300 V/Hr/V to about 1500V/Hr/V, at temperatures ranging from about 160° C. to about 290° C.,preferably from about 190° C. to about 260° C., and pressures aboveabout 80 psig, preferably ranging from about 80 psig to about 600 psig,more preferably from about 140 psig to about 400 psig.

The product of either the methanol conversion reaction, or synthesisreaction generally and preferably contains 45 percent or greater, morepreferably 60 percent or greater, C₁₀ +liquid hydrocarbons which boilabove 160° C. (320° F.).

In forming the catalyst, titania is used as a support, or in combinationwith other materials for forming a support. The titania used for thesupport in either methanol or syngas conversions, however, is preferablyone where the rutile:anatase ratio is at least about 2:3 as determinedby x-ray diffraction (ASTM D 3720-78). Preferably, the titania used forthe catalyst support of catalysts used in syngas conversion is onewherein the rutile:anatase ratio is at least about 3:2. Suitably thetitania used for syngas conversions is one containing a rutile:anataseratio of form about 3:2 to about 100:1, or higher, preferably from about4:1 to about 100:1, or higher. A preferred, and more selective catalystfor use in methanol conversion reactions is one containing titaniawherein the rutile:anatase ranges from about 2:3 to about 3:2. Thesurface area of such forms of titania are less than about 50 m² /g. Thisweight of rutile provides generally optimum activity, and C₁₀+hydrocarbon selectivity without significant gas and CO₂ make.

The zirconium, hafnium, cerium, or uranium promoted cobalt-titaniacatalyst prior to regeneration, it was found, will have essentially thesame high activity as the corresponding unpromoted cobalt-titaniacatalyst. Thus, during an initial, on-oil operating run, or run whereinhydrocarbons are being produced over the fresh catalyst by methanolconversion or hydrocarbon synthesis from carbon monoxide and hydrogenthe activity of the two different catalysts is not essentiallydifferent. Unlike an unpromoted cobalt-titania catalyst, or catalystotherwise similar except that it does not contain zirconium, hafnium,cerium, or uranium, however, the initial high activity of the promotedcobalt-titania catalyst will be maintained even after regeneration ofthe coked catalyst which is accomplished by burning off the cokedeposits at elevated temperature in an oxygen-containing gas (e.g.,air), and the catalyst then reduced, as by contact of the catalyst withhydrogen, or a hydrogen-containing gas. Moreover, the stability of thepromoted cobalt-catalyst will be maintained, this catalyst deactivatingin an on-oil run at corresponding conditions at no greater rate thanthat of any unpromoted cobalt-titania catalyst, or catalyst otherwisesimilar except that it does not contain zirconium, hafnium, cerium, oruranium, which has never been regenerated. Whereas the unpromoted, freshcobalt-titania catalyst was thus found to possess an initial highactivity in an on-oil operation, it was subsequently found that theactivity of this catalyst was not completely restored afterregeneration, the catalyst recovering only about 50 percent of theactivity formerly possessed by the fresh catalyst. Moreover, afterinitiation of an on-oil operation, the activity of the regeneratedzirconium, hafnium, cerium, or uranium promoted cobalt-titania willdecline at about the same rate as that of the fresh unpromotedcobalt-titania catalyst. Retention of this activity and stability by thepromoted cobalt-titania catalysts thus effectively eliminates thedisadvantages formerly associated with unpromoted cobalt-titaniacatalysts, and makes possible full utilization of cobalt-titaniacatalysts in commercial operations.

Cobalt-titania catalysts, like most hydrocarbon synthesis catalysts areprimarly deactivated during on-oil operation by the deposition thereonof a carbonaceous residue, i.e., coke, formed either during extendedperiods of operation or during feed or temperature upsets. It wasthought that the coked catalyst could be regenerated and its initialactivity restored by burning the coke from the catalyst. Air burns at,e.g., 400°-500° C., are thus normally effective in removing essentiallyall of the carbon from a catalyst, this offering a relatively simple,commercially feasible technique for regenerating deactivatedcobalt-titania catalysts. However, in order for air regeneration torestore activity, the catalytic cobalt metal must be maintained indispersed state at both on-oil and regeneration conditions. Albeit theunpromoted cobalt catalyst upon which the cobalt was well dispersed wasfound to be stable during an on-oil operation, the cobalt agglomeratedduring high temperature air treatment. It is found however, that even inlow concentration, zirconium, hafnium, cerium, or uranium, or admixturethereof, could be used as an additive to stabilize the cobalt-titaniacatalyst not only by maintaining the cobalt in a dispersed state uponthe titania during on-oil operations, but also during air burns, thusproviding a readily regenerable catalyst.

Whereas Applicants do not wish to be bound by any specific mechanistictheory, it is believed that the action of the zirconium, hafnium,cerium, or uranium metals in promoting the regenerability of acobalt-titania catalyst during an air burn can be explained, at least inpart. Thus, during an air burn the crystallites of metallic cobalt of acobalt-titania catalyst are oxidized to form Co₃ O₄ which agglomeratesat temperatures above about 350° C. After reactivation of the catalystby contact with hydrogen cobalt metal agglomerates are formed which areof larger crystallite size than the original metallic crystallites ofcobalt metal. Large agglomerates of cobalt form catalysts which are lessactive than catalysts formed with more finely dispersed cobalt. Thezirconium, hafnium, cerium, or uranium promoter metals of the promotedcobalt-titania catalyst are present as highly dispersed oxides over theTiO₂ support surface, and all are of a cubic crystal structure (exceptfor Ce which can exist either as cubic CeO₂, or hexagonal Ce₂ O₃). Theseoxides are believed to form a strong surface interaction with Co₃ O₄which is also of cubic crystal structure. The cubic oxide promoters arethus believed to form a matrix, or act as a "glue" between the Co₃ O₄and TiO₂, and maintain the cobalt in finely dispersed form upon thesupport surface.

The catalysts of this invention may be prepared by techniques known inthe art for the preparation of other catalysts. The catalyst can, e.g.,be prepared by gellation, or cogellation techniques. Suitably, however,the cobalt, zirconium, hafnium, cerium, or uranium metals, or admixturesof these metals with each other, or with other metals, can be depositedon a previously pilled, pelleted, beaded, extruded, or sieved supportmaterial by the impregnation method. In preparing catalysts, the metalsare deposited from solution on the support in preselected amounts toprovide the desired absolute amounts, and weight ratio of the respectivemetals, e.g., cobalt and zirconium or hafnium, or cobalt and anadmixture of zirconium and hafnium. Suitably, the cobalt and zirconium,hafnium, cerium, or uranium metals are composited with the support bycontacting the support with a solution of a cobalt-containing compound,or salt, e.g., cobalt nitrate, acetate, acetylacetonate, napthenate,carbonyl, or the like, and a promoter metal-containing compound, orsalt. One metal can be composited with the support, and then the other.For example, the promoter metal can first be impregnated upon thesupport, followed by impregnation of the cobalt, or vice versa.Optionally, the promoter metal and cobalt can be coimpregnated upon thesupport. The cobalt and promoter metal compounds used in theimpregnation can be any organometallic or inorganic compounds which willdecompose to give cobalt, and zirconium, hafnium, cerium, or uraniumoxides upon calcination, e.g., a cobalt, zirconium, or hafnium nitrate,acetate, acetylacetonate, naphthenate, carbonyl, or the like. The amountof impregnation solution used should be sufficient to completely immersethe carrier, usually within the range from about 1 to 20 times of thecarrier by volume, depending on the metal, or metals, concentration inthe impregnation solution. The impregnation treatment can be carried outunder a wide range of conditions including ambient or elevatedtemperatures. Metal components other than cobalt and a promoter metal,or metals, can also be added. The introduction of an additional metal,or metals, into the catalyst can be carried out by any method and at anytime of the catalyst preparation, for example, prior to, following, orsimultaneously with the impregnation of the support with the cobalt andzirconium, hafnium, cerium, or uranium metal components. In the usualoperation, the additional component is introduced simultaneously withthe incorporation of the cobalt and the zirconium, and hafnium, cerium,or uranium components.

It is preferred to first impregnate the zirconium, hafnium, cerium, oruranium metal, or metals onto the support, or to coimpregnate thezirconium, hafnium, cerium, or uranium metal, or metal with the cobaltinto the titania support, and then to dry and calcine the catalyst.Thus, in one technique for preparing a catalyst a titania, ortitania-containing support, is first impregnated with the zirconium,hafnium, cerium, or uranium metal salt, or compound, and then dried orcalcined at conventional conditions. Cobalt is then dispersed on theprecalcined support on which the zirconium, hafnium, cerium, or uraniummetal, or metals, has been dispersed and the catalyst again dried, andcalcined. Or, the zirconium, hafnium, cerium, or uranium metal, ormetals, may be coimpregnated onto the support, and the catalyst thendried, and calcined. The zirconium, hafnium, cerium and uranium metalsare believed to exist in the finished freshly calcined catalyst as anoxide, the metal oxides being more closely associated with the titaniasupport than with the cobalt.

The promoted cobalt-titania catalyst, after impregnation of the support,is dried by heating at a temperature above about 30° C., preferablybetween 30° C. and 125° C., in the presence of nitrogen or oxygen, orboth, or air, in a gas stream or under vacuum. It is necessary toactivate the finished catalyst prior to use. Preferably, the catalyst iscontacted in a first step with oxygen, air, or other oxygen-containinggas at temperature sufficient to oxidize the cobalt, and convert thecobalt to Co₃ O₄. Temperatures ranging above about 150° C., andpreferably above about 200° C., are satisfactory to convert the cobaltto the oxide, but temperatures up to about 500° C., such as might beused in the regeneration of a severely deactivated catalyst, can betolerated. Suitably, the oxidation of the cobalt is achieved attemperatures ranging from about 150° C. to about 300° C. The cobaltoxide contained on the catalyst is then reduced to cobalt metal toactivate the catalyst. Reduction is performed by contact of thecatalyst, whether or not previously oxidized, with a reducing gas,suitably with hydrogen or a hydrogen-containing gas stream attemperatures above about 250° C.; preferably above about 300° C.Suitably, the catalyst is reduced at temperatures ranging from about250° C. to about 500° C., and preferably from about 300° C. to about450° C., for periods ranging from about 0.5 to about 24 hours atpressures ranging from ambient to about 40 atmospheres. Hydrogen, or agas containing hydrogen and inert components in admixture issatisfactory for use in carrying out the reduction.

In the regeneration step, the coke is burned from the catalyst. Thecatalyst can be contacted with a dilute oxygen-containing gas and thecoke burned from the catalyst at controlled temperature below thesintering temperature of the catalyst. The temperature of the burn ismaintained at the desired level by controlling the oxygen concentrationand inlet gas temperature, this taking into consideration the amount ofcoke to be removed and the time desired to complete the burn. Generally,the catalyst is treated with a gas having an oxygen partial pressureabove about 0.1 pounds per square inch (psi), and preferably in therange of from about 0.3 psi to about 2.0 psi, to provide a temperatureranging from about 300° C. to about 550° C., at static or dynamicconditions, preferably the latter, for a time sufficient to remove thecoke deposits. Coke burn-off can be accomplished by first introducingonly enough oxygen to initiate the burn while maintaining a temperatureon the low side of this range, and gradually increasing the temperatureas the flame front is advanced by additional oxygen injection until thetemperature has reached optimum. Most of the coke can generally beremoved in this way. The catalyst is then reactivated by treatment withhydrogen or hydrogen-containing gas as with a fresh catalyst.

The invention will be more fully understood by reference to thefollowing demonstrations and examples which present comparative dataillustrating its more salient features. All parts are given in terms ofweight except as otherwise specified. Feed compositions are expressed asmolar ratios of the components.

The addition of a small amount of hafnium, zirconium, cerium, oruranium, respectively, to a Co-TiO₂ catalyst maintains the cobalt in ahigh state of dispersion and stabilizes the catalyst during hightemperature air treatments. The added zirconium, hafnium, cerium, oruranium metal thus maintains during and after regeneration the very highintrinsic activity of the catalyst which is characteristic of a freshcatalyst having well-dispersed cobalt on the TiO₂. The high intrinsicactivity of the promoted Co-TiO₂ permits, after regeneration, the samehigh conversion operations at low temperature, where excellentselectivity is obtained in the conversion of methanol or syngas to C₁₀+hydrocarbons as with a fresh catalyst.

In the following example, the results of a series of runs are givenwherein various metals, inclusive of zirconium, hafnium, cerium, anduranium, respectively, were added to portions of a freshly preparedCo-TiO₂ catalyst, these specimens of catalyst being compared with aportion of the Co-TiO₂ catalyst to which no promoter metal was added.These catalysts were calcined by contact with air at elevatedtemperature in a simulated coke burn, activated by contact withhydrogen, and then employed in a Fischer-Tropsch reaction. The metalimpregnated catalysts are compared with the control, or portion of theCo-TiO₂ catalyst similarly treated except that no promoter metal wasadded thereto. The effectiveness of the metal added to the Co-TiO₂catalyst, or metal promoter, is demonstrated by the amount of COconversion obtained with each of the catalysts after the simulatedregeneration.

EXAMPLE 1

Titania (Degussa P-25 TiO₂) was used as the support for preparation ofseveral catalysts. The Degussa P-25 TiO₂ was admixed with Sterotex (avegetable stearine used as a lubricant; a product of Capital CityProducts Co.) and, after pilling, grinding, screening to 80-150 mesh(Tyler), was calcined in air at 650° C. for 16 hours to give TiO₂supports with the following properties:

    ______________________________________                                        Rutile:Anatase Surface Area                                                                             Pore Volume                                         Weight Ratio.sup.(1)                                                                         m.sup.2 /g ml/g                                                ______________________________________                                        97:3           14         0.16                                                ______________________________________                                         .sup.(1) ASTM D 372078.                                                  

A series of promoted 11% Co-TiO₂ catalysts was prepared by impregnationof the TiO₂ support using a rotary evaporator as described below, andthese compared with an unpromoted 11% Co-TiO₂ catalyst in conducting ahydrocarbon synthesis operation.

The promoter metals were applied to the TiO₂ support simultaneously withthe cobalt, the impregnating solvent used being acetone, acetone/15-20%H₂ O, or water (Preparation A, B, or C), or by sequential impregnationfrom solution of a promoter metal, with intermediate air treatment attemperatures ranging from 140° C. to 500° C., with a final impregnationof the dried promoter-containing TiO₂ composite with a solution ofcobaltous nitrate (Preparations D, E, F, G, and H). These catalystpreparation procedures are described below in Table I.

                  TABLE I                                                         ______________________________________                                        Catalyst Preparation Procedures                                               ______________________________________                                        Simultaneous Impregnations                                                                        Solvent                                                   ______________________________________                                        A                   Acetone                                                   B                   Acetone/15-20% H.sub.2 O                                  C                   H.sub.2 O                                                 ______________________________________                                                                         Solvent                                                            Intermediate                                                                             for 2nd                                      Sequential                                                                            Solvent for 1st                                                                             Air Treat  Impregnation                                 Impreg- Impregnation  Temperature                                                                              (Cobalt                                      nations (Promoter)    °C. Nitrate)                                     ______________________________________                                        D       Isopropanol   140        Acetone                                      E       Acetone/15% H.sub.2 O                                                                       140        Acetone                                      F       Acetone/15% H.sub.2 O                                                                       500        Acetone                                      G       H.sub.2 O     140        Acetone                                      H       H.sub.2 O     500        H.sub.2 O                                    ______________________________________                                    

Catalysts impregnated in this manner were dried in a vacuum oven at 140°C. for about 20 hours. Air treatments were made in forced-air ovens atvarious temperatures for 3 hours. The catalysts were diluted 1:1 byvolume with 80-150 mesh TiO₂ (to minimize temperature gradients),charged to a 1/4 inch ID reactor tube, reduced in H₂ at 450° C., 5000V/Hr/V catalyst for one hour, and then reacted with syngas at 200° C.,280 psig, GHSV=1500 (on catalyst), and H₂ /CO=2 for at least 16 hours.The performance of each catalyst was monitored by conventional GCanalysis using neon as an internal standard (4% in the feed). Activityresults are tabulated in Table II and shown in graphical form in FIGS. 1and 2. High selectivity to heavy paraffinic hydrocarbons was obtainedover all of these Co-TiO₂ catalysts independent of the promoterspresent. Thus, methane selectivity was about 3-5 mol. % and CO₂selectivity was less than about 0.2 mol. % in all runs. The balance ofthe product was C₂ +hydrocarbons.

                  TABLE II                                                        ______________________________________                                        Results of Catalyst Tests                                                                         Prep.   Air Treat                                                                              % CO                                     Promoter on 11% Co--TiO.sub.2                                                                     Pro-    Temp.    Con-                                     Element                                                                              Compound     Wt. %   cedure                                                                              °C. 3 Hr.                                                                     version                              ______________________________________                                        None   --           --      A     --     78                                                               "     250    73                                                               "     400    63                                                               "     500    48                                                               "     550    32                                                               "     600    28                                   Hf     HfO(NO.sub.3).sub.2                                                                        0.06    A     500    48                                          "            0.31    "     400    78                                          "            0.31    "     500    73                                          "            0.50    "     500    70                                          "            0.50    "     600    58                                          "            0.63    "     500    71                                          "            1.89    "     500    78                                          "            3.0     "     500    81                                   Ce     (NH.sub.4).sub.2 Ce(NO.sub.3).sub.6                                                        0.5     B     --     79                                          "            0.5     B     500    81                                          "            0.5     E     500    78                                          "            0.5     F     500    76                                          "            0.5     B     600    63                                          "            2.0     B     500    64                                          "            2.0     H     500    61                                   Zr     Zr(OC.sub.3 H.sub.7).sub.4                                                                 0.5     D     --     85                                          "            0.5     D     500    81                                          ZrO(O.sub.2 CCH.sub.3).sub.2                                                               0.3     G     --     75                                          "            0.3     C     --     75                                          "            0.3     C     500    63                                          "            0.6     C     500    68                                          "            0.9     C     --     80                                          "            0.9     C     500    70                                          "            1.1     C     500    74                                   U      UO.sub.2 (NO.sub.3).sub.2                                                                  1.0     A     500    79                                   ______________________________________                                    

It is clear from these results, as depicted by reference to FIG. 1, thatthe zirconium, hafnium, cerium, or uranium promote, and maintain theactivity of the 11% Co-TiO₂ catalyst after calcination. The activity ofpromoted 11% Co-TiO₂ thus remains high and virtually constant aftercalcination as high as 500° C. whereas, in contrast, the activity of theunpromoted 11% Co-TiO₂ catalyst declines rapidly, and sharply; the rateof activity decreasing dependent upon the temperature of calcination.

The data depicted in FIG. 2 clearly show the effectiveness of smallamounts of zirconium, hafnium, cerium, and uranium to enhance theregenerability of a 11% Co-TiO₂ catalyst, promoters in concentration ofabout 0.5 wt. percent being adequate for near-maximum stabilization.Promoters in greater concentration do not appear to produce anysignificant additional benefit, if any.

The hydrocarbon product distribution was further defined in a run of an11.2% Co-0.5% Hf-TiO₂ catalyst. The catalyst (150 cc) was diluted with110 cc TiO₂, charged to a 1/2 inch ID reactor, reduced with H₂ at 450°C. for 4 hours, and then used for the conversion of syngas tohydrocarbons. Operating conditions and product distribution data areshown in Table III. The results confirm the formation of very heavyhydrocarbons over Co-Hf-TiO₂ catalyst.

                  TABLE III                                                       ______________________________________                                        Hydrocarbon Product Distribution From Co--Hf--TiO.sub.2                       ______________________________________                                        Temperature °C.                                                        Sandbath                204                                                   Reactor Average         206                                                   Gas Hourly Space Velocity on catalyst                                                                 1000                                                  Pressure, psig          280                                                   H.sub.2 /CO Inlet Ratio 2.09                                                  % CO Conversion         89                                                    Hydrocarbon Product Distribution, Wt. %                                       C.sub.1                 5.6                                                   C.sub.2 -C.sub.4        3.4                                                   C.sub.5 -550° F. 15.1                                                  550-700° F.      10.0                                                  700-1050° F.     29.2                                                  1050° F..sup.+   36.7                                                  ______________________________________                                    

The following example illustrates the catalysts of this invention usedfor the conversion of methanol to hydrocarbons.

EXAMPLE 2

Titania in the form of spherical beads was supplied by a catalystmanufacturer and employed to make catalysts. The titania was of 14-20mesh size (Tyler), and characterized as having a rutile:anatase ratio of86:14, a surface area of 17 m² /g, and pore volume of 0.11 ml/gm.Catalysts were prepared from portions of the titania by simultaneousimpregnation with aqueous solutions containing cobalt nitrate and a saltof ZrO(O₂ CCH₃)₂, HfO(NO₃)₂, (NH₄)₂ Ce(NO₃)₆ and UO₂ (NO₃)₂,respectively. Each catalyst, after impregnation, was dried and airtreated at 500° C. for three hours. The composition of each of thesecatalysts in terms of weight percent cobalt and weight percentconcentration of the promoter (1 wt. %) is given in Table IV.

In separate runs, each of the promoted Co-TiO₂ catalysts were charged toa 3/8 inch ID reactor tube, reduced in hydrogen at 450° C., 1000 GHSV,and 0 psig for one hour. A feed admixture of hydrogen, argon, andmethanol in molar ratio of 20 CH₃ OH:1H₂ :4Ar at CH₃ OH LHSV=0.67, 230°C. and 400 psig was then passed over each of the catalysts. Theperformance of each catalyst was monitored by conventional GC analysisof the product with the results given in Table IV.

                  TABLE IV                                                        ______________________________________                                         CONVERSION OF METHANOL TO HYDROCARBONS                                       (230° C., 400 PSIG, LHSV = 0.67, 20 CH.sub.3 OH:1H.sub.2 :4            ______________________________________                                        Ar)                                                                           Catalyst Composition on TiO.sub.2                                             Wt. % Co         5.00    4.34   4.65 4.55 4.73                                Promoter (1 Wt. %)                                                                             None    Zr     Hf   Ce   U                                   % CH.sub.3 OH Conversion                                                                       31      37     34   49   46                                  Rate, g CH.sub.3 OH Converted/                                                                 1.6     2.3    1.9  2.8  2.6                                 hr./g Co                                                                      Carbon Product                                                                Distribution, Wt. %                                                           CO               16      13     16   10   9                                   CO.sub.2         8       9      7    9    13                                  CH.sub.4         8       8      8    7    9                                   C.sub.2.sup.+    68      70     69   74   69                                  ______________________________________                                    

The results show that the promoted catalysts are more active thanunpromoted Co-TiO₂ catalysts, calcined at 500° C.; which is best shownby the methanol conversion rate. Cerium, as will be observed, is anespecially good promoter for methanol conversion, the cerium promotedCo-TiO₂ catalyst giving the highest activity and best selectivity to C₂+hydrocarbons. The selectivity of the Co-TiO₂ catalyst generally byaddition thereto of the respective promoter remains high, and to someextent improved by the presence of the promoter.

It is apparent that various modifications and changes can be madewithout departing the spirit and scope of the present invention.

What is claimed is:
 1. A process useful for the conversion of methanolto hydrocarbons which comprises contacting said methanol at reactionconditions with a catalyst which comprises from about 2 percent to about25 percent cobalt, based on the weight of the catalyst composition,composited with titania, or a titania-containing support, to which isadded a zirconium, hafnium, cerium, or uranium promoter, the weightratio of the zirconium, hafnium, cerium, or uranium metal:cobalt beinggreater than about 0.010:1; said reaction conditions being definedwithin ranges as follows:Methanol:H₂ ratio: greater than about 4:1 SpaceVelocities, hr⁻¹ : about 0.1 to 10 Temperatures, °C.: about 150 to 350Methanol Partial Pressure, psia: about 100 to
 1000. 2. The process ofclaim 1 wherein the weight ratio of the zirconium, hafnium, cerium, oruranium metal:cobalt ranges from about 0.04:1 to about 0.25:1.
 3. Theprocess of claim 1 wherein said promoter is hafnium.
 4. The process ofclaim 1 wherein said promoter is zirconium.
 5. The process of claim 1wherein the catalyst contains from about 5 to about 15 percent cobalt,based on the weight of the catalyst compositions.
 6. A process usefulfor the conversion of methanol to hydrocarbons which comprisescontacting said methanol at reaction conditions with a catalyst whichcomprises cobalt in catalytically active amount composited with titania,or a titania-containing support, to which is added sufficient of azirconium, hafnium, cerium, or uranium promoter to obtain, on conversionof methanol to hydrocarbons with deposition of coke on the catalyst, andthe catalyst is regenerated by burning coke therefrom and thenreactivated by contact with a reducing gas to reduce the cobalt, anactivity, and activity maintenance at corresponding reaction conditionsapproximating that of a catalyst otherwise similar except that thecobalt-titania catalyst does not contain the added promoter, and has notbeen regenerated; said reaction conditions being defined within rangesas follows:Methanol:H₂ ratio: greater than about 4:1 Space Velocities,hr⁻¹ : about 0.1 to 10 Temperatures, °C.: about 150 to 350 MethanolPartial Pressure, psia: about 100 to 1000.